Author Topic: Car stutters and dies after 20-30 minutes  (Read 577 times)

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Offline Andy78TA

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Car stutters and dies after 20-30 minutes
« on: May 04, 2020, 05:43:05 PM »
Hi All,

Haven't been on here in a while, but back to working on the car and have a weird issue. I have been driving my car this spring without issue and than randomly this weekend I had it out idling in the driveway for a while and it started acting funny. In Park it would decrease rpms to almost stalling out and then would recover. It only did this after it was sitting out idling for 20 minutes or more. I didn't think much of it, but when I took it for a drive it really started to act up. It was fine when I had the RPMS above 1500 or so and cruising, but then I got to a stop sign and it actually stalled out on me and wouldn't start right back up, I had to crank it a little more than usual, but eventually did restart.

I thought it was a carb issue, so I swapped carbs since I had a second one, but the same thing is happening. I recently added a fuel pressure regulator and new fuel pump, a vacuum canister, and new plugs and wires and didn't have any issues after installing each, but now something is definitely off.

Can someone point me to some things to look at? I really thought it was a carb issue, but that doesn't make much sense if it happens with both, right?

Thanks all!
78 T/A pontiac 400- Custom Headers - 2.5 Pypes Violator header back system - Edlebrock Performer Intake - Edelbrock 1413 Carb - Head work - pro comp roller rocker - CVF bracket and pulley kit - Custom system - Recaro T/A interior

Offline Aus78Formula

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Re: Car stutters and dies after 20-30 minutes
« Reply #1 on: May 04, 2020, 11:54:29 PM »
All those things swapped are since the issue, trying to locate it? What about the fuel cap being the correct type? And how recent has the fuel filter sock in tank been done?

Offline Maxthe222

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Re: Car stutters and dies after 20-30 minutes
« Reply #2 on: May 05, 2020, 11:21:50 PM »
Had the same thing with my '79 403. Unless you kept your foot on the pedal it'd conk out at a stop sign or stationary. Combination of timing and carb adjustment. Give the timing a check and check your carb idle.
'79 Y84 WS6 T/A
'79 W72 WS6 F/A
'71 FRMLA 400/4-Spd

Offline jerry455

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Re: Car stutters and dies after 20-30 minutes
« Reply #3 on: May 06, 2020, 07:30:15 PM »
I had a similar problem last spring after sitting all winter. When it was warmer the car would idle low and almost stall. I drove it for a while like this and when I put fresh fuel in it ran better almost instantly. I think it was the winter fuel used in the warm spring that was causing the problem. I know there are summer and winter fuels around here and the vapor pressure is different. It sure made a difference on my car. Check your ignition. Electronic ignition module could be breaking down with the increased heat.